Peace,
A prosthodontist has 2 to 3 years more trainging beyond dental school. They learn how to restore function in very difficult cases. They tend to deal wtih the whole mouth in cases that have had extensive destruction of the teeth, surgery to the jaws and supporting structures post cancer treatment or post surgery.
We are all capable of treateing theses cases however, prosthodontists pretty much stick to this type of whole mouth rehabilitation as opposed to treating simple healthy one or two teeth cases.
It's a little more involved than that but that is the long and the short of it.
Hope all is getting better.
Cheers,
Mike